Interventional or surgical procedures performed with the aid of x-ray systems are required for numerous medical examinations or treatments. Radiological interventions are thus frequently undertaken for the diagnosis or treatment of vascular diseases, in which an instrument, especially a catheter, is fed through a peripheral blood vessel using x-ray illumination to the point of interest in the body. Controlling this type of instrument can sometimes be very demanding, especially if the blood vessels are very damaged and have many branches. To improve the navigation for the examining doctor this type of intervention is monitored as a rule with a monoplanar or biplanar imaging x-ray system. The x-ray images displayed during the intervention can in such cases map the position of the instruments, for example catheters, guide wires or stents, very exactly. With a suitable image processing method the position of the instrument can also be determined precisely.
When a monoplanar x-ray system is used however, the position of the instruments can only be determined in two dimensions. The three-dimensional position is unknown. The knowledge about the three-dimensional position of the instruments is however desirable in cases in which this position is to be displayed in an image representation of a 3D image data record which was previously recorded with a corresponding imaging modality. This type of overlaid display is of advantage for navigating the instrument.
Previously at least two x-ray images from different directions of projection have been required to determine the 3D position of an instrument or the tip of a catheter, as is described for example in US 2003/0220555 A1. This demands either the use of an expensive biplanar x-ray system or a time-consuming change in the angulation of a monoplanar x-ray system in conjunction with a sequential recording of two x-ray images from different directions.
A further previously known option for three-dimensional position determination of instruments demands the use of specific localization systems, employing electromagnetic sensors for example. A disadvantage of this method compared to x-ray imaging lies in the fact that only instruments equipped with specific sensors can be localized. Furthermore the number of instruments able to be localized as well as the number of sensors per instrument is restricted with these types of localization systems.